6.5l td drivability issue's

[MrMarty51]

Have You checked the vacuum from the vacuum pump ?

 

[Budd Comeau]

Have You checked the vacuum from the vacuum pump ?

That's probably the only thing I have not done.
Silly question, where's it located at.
Because I'm not sure where to look at.

1999 C3500 6.5L turbo 5spd 2wd 1ton.

 

[ak diesel driver]

This may sound strange but do you have any other electrical issues?. Wondering about a faulty IGN switch. Might be giving the PCM low or intermittent power.

 

[Budd Comeau]

This may sound strange but do you have any other electrical issues?. Wondering about a faulty IGN switch. Might be giving the PCM low or intermittent power.

Not to my knowledge.
All gauges work.
No light issues.

1999 C3500 6.5L turbo 5spd 2wd 1ton.

 

[ak diesel driver]

Try putting a voltmeter on the wire going to the PCM and see if it fluctuates.

 

[GM Guy]

I am chasing similar issues on my 98 K2500, and I would recommend at least trying an ignition switch before writing off the ECM.

That said, ignition switch didint fix mine, but hopefully it will fix yours.

 

[Husker6.5]

Any progress on this?

 

[FellowTraveler]

I had a strange issue once and found the harness to the computer is under the front passenger foot well that was the issue from passengers placing their feet up and stretching out which in turn pulled some pin connectors out of their plugs "some were making intermittent contact while other lost contact."

Another place to check the harness is behind and above the engine as vibration and even heat can cause damage.

 

[Budd Comeau]

Any progress on this?

Yes,
It turned out to be a fuel cell and sending unit issue.
Replaced full cell and sending unit.

All is well that ends well.